Cation exchangers or chelating agents and process for the preparation thereof

ABSTRACT

A cation exchanger or a chelating agent having at least structural units represented by the following formula (I), the structural units being derived from a crosslinkable monomer containing an unsaturated hydrocarbon group:                    
     wherein A represents a C 3 -C 8  alkylene group or a C 4 -C 9  alkoxymethylene group; L represents SO 3   − X + , where X +  is a counter ion coordinated with the SO 3   −  group, or a chelate-forming functional group; and the benzene ring may be substituted with an alkyl group or a halogen atom.

TECHNICAL FIELD

The present invention relates to a cation exchanger or chelating agentand a production process thereof. The cation exchanger of the presentinvention has a novel structure with excellent heat resistance and otherfeatures, and the chelating agent of the present invention has a novelstructure with excellent chelate forming ability, heat resistance andother features.

BACKGROUND ART

Generally, cation exchange resins are produced by sulfonatingstyrene-divinylbenzene copolymers with sulfuric acid and/or sulfurtrioxide of various concentrations in view of chemical stability of theproduced resins, their strength and production cost. There are alsoknown the cation exchange resins produced by introducing a sulfonicgroup to the terminal of acrylic derivative resins, but these cationexchange resins are poor in chemical stability.

As another exemplification of cation exchange resins, in U.S. Pat. No.3,944,507 specification, there has been described a cation exchangerincorporated with methylene linkage (benzenesulfonic acid structure),but this cation exchanger is unsatisfactory in heat resistance. Therehas also been described a cation exchanger produced by introducing ahalogen atom into the benzene ring for improving heat resistance, butthis cation exchanger has not been commercially produced and usedbecause of liability to ion leakage of its halides such as chlorinatedor brominated products.

On the other hand, chelating agents (resins) are the functional resinsproduced by introducing functional groups capable of forming metal ionsand chelates to the crosslinked polymers, and a variety of chelateresins have been proposed according to the type of the chelate-formingfunctional group used. Typical examples of the chelate-formingfunctional groups usable for the above purpose are iminodiacetic acidgroup (—N(CH₂COO—)₂) and polyamine group (—NH(CH₂CH₂NH)n.H). Thesechelate resins, for example, the said iminodiacetic acid type chelateresins are usually produced by converting the halogen of a crosslinkedpolymer containing halogenated methylstyrene into iminodiacetic acidgroup.

It appears, however, that most of the conventional proposals relating tochelate resins are directed to the improvement of chelate-formingfunctional groups and no sufficient proposals have been made on thestructure between the crosslinked polymer and the chelate-formingfunctional group.

The present invention has been made in view of the above circumstances,and an object thereof is to provide a cation exchanger which hasexcellent heat resistance and high reaction rate, is capable ofminimized elution from the polymer, and a process for producing such acation exchanger. Another object of the present invention is to providea chelating agent of a novel structure having excellent chelate formingability and heat resistance, and a process for producing such achelating agent.

DISCLOSURE OF THE INVENTION

An object of the present invention can be attained by a cation exchangeror a chelating agent having at least structural units represented by thefollowing formula (I), the structural units being derived from acrosslinkable monomer containing an unsaturated hydrocarbon group:

wherein A represents a C₃-C₈ alkylene group or a C₄-C₉ alkoxymethylenegroup; L represents SO₃ ⁻X⁺, where X⁺ is a counter ion coordinated withthe SO₃ ⁻ group, or a chelate-forming functional group; and the benzenering may be substituted with an alkyl group or a halogen atom.

Another object of the present invention can be accomplished by a processfor producing a cation exchanger as defined in the above first aspect,which comprises suspension-polymerizing at least a precursor monomerhaving the structural units represented by the following formula (II)and a crosslinkable monomer having an unsaturated hydrocarbon group inthe presence of a polymerization initiator, and if necessary introducinga cation exchange group into the obtained spherical crosslinked polymer:

wherein A has the same meaning as defined in the formula (I); Z¹represents chlorine, bromine, iodine, a hydroxyl group, a tosyl group(toluenesulfonic group), a thiol group or a sulfonic group; and thebenzene ring may be substituted with an alkyl group or a halogen atom.

Still another object of the present invention can be achieved by aprocess for producing a chelating agent as defined in the above firstaspect, which comprises suspension-polymerizing at least a precursormonomer having the structural units represented by the following formula(III) and a crosslinkable monomer having an unsaturated hydrocarbongroup in the presence of a polymerization initiator, and introducing achelate-forming functional group into the obtained spherical crosslinkedpolymer:

wherein A has the same meaning as defined in the formula (I); Z²represents chlorine, bromine; iodine or a hydroxyl group; and thebenzene ring may be substituted with an alkyl group or a halogen atom.

The present invention is described in detail below.

First, the cation exchanger or chelating agent according to the presentinvention is explained.

The cation exchanger or chelating agent of the present invention has atleast the structural units represented by the above-shown formula (I)and the structural units derived from a crosslinkable monomer having anunsaturated hydrocarbon group.

In case where L in the formula (I) is SO₃ ⁻X⁻ (wherein X⁺ is a counterion coordinated with the SO₃ ⁻ group), a cation exchanger is provided;and in case where L is a chelate-forming functional group, a chelatingagent is provided.

L representing a chelate-forming functional group is not specified, andany functional group used in the known chelate resins can be usedwithout restrictions. Typical examples of L include iminodiacetate group(—N(CH₂COO—)₂), polyamine group (—NH(CH₂CH₂NH)_(n).H), dimethylglycine(dimethylaminoacetate) group (—N⁺(CH₃)₂CH₂COO—) and the like. Ascompared with, for example, aminomethylsulfonic group disclosed inJapanese Patent KOHYO (Laid-Open PCT Application) No. 4-500223, it isparticularly remarkable that these chelate-forming functional groups,are relatively simple in structure, advantageous in cost and alsosusceptible to the influence of benzene ring because of relativelysimple molecular structure, so that the effect by spacer (A) in thepresent invention, which is described later, is remarkable.

Besides the above-mentioned, there can also be used aminophosphoricgroup and phosphonic group as the chelate-forming functional group. Theaminophosphoric type chelate resins can, for instance, be preferablyused for purification of salt water contained in the raw materials ofelectrolytic sodium hydroxide and are capable of effectively removingthe impurities such as calcium and strontium in the salt water. On theother hand, the phosphonic type chelate resins show high adsorptivityfor many types of metal ions and have higher selectivity for tri- andtetravalent metal ions than for mono- and divalent metal ions. Becauseof these properties, the phosphonic chelate resins are advantageouslyused for selective removal of iron ions in zinc or nickel electroplatingsolutions and for separation and concentration of uranium and rare earthelement ions.

In the formula (I), A represents an alkylene group having 3 to 8 carbonatoms or an alkoxymethylene group having 4 to 9 carbon atoms. Examplesof the C₃-C₈ alkylene groups include propylene, butylene, pentylene,hexylene and octylene, and examples of the C₄-C₉ alkoxymethylene groupsinclude butoxymethylene and pentoxymethylene. The C₃-C₈ alkylene groupsmay be either straight-chain alkylene groups such as mentioned above orbranched alkylene groups such as isopropyl and t-butyl groups. When A isan alkylene group, it is preferably a straight-chain alkylene grouphaving 3 to 8 carbon atoms, more preferably the one having 3 to 6 carbonatoms. When A is an alkoxymethylene group, it is preferably the onehaving 5 to 7 carbon atoms.

Japanese Patent KOHYO (Laid-Open PCT Application) No. 4-500223 hasproposed a process for producing aminomethylphosphonic chelate resins byintroducing a functional group represented by the formula—(CHR¹)m—NR²—CH₂—PO₃R³R⁴ (wherein R¹ includes hydrogen and m is a numberof 1 to 12) into a crosslinked polymer. However, the chelate resinsdescribed concretely in the above patent, for example, the chelateresins mentioned in all of the Examples 1-27 are the ones obtainable byintroducing an aminomethylphosphonic group into a chloromethylatedcrosslinked polymer which is a compound of the formula (I) wherein m is1.

In the present invention, when A does not satisfy the above definition,there are the following problems for both of cation exchanger andchelating agent.

When A is a Short-Chain Group Like Methylene or Ethylene

(1) Cation exchange group (SO₃ ⁻ group) is subject to the influence ofbenzene ring through the short chain, and consequently no satisfactoryheat resistance may be obtained and also acidity lowers. Reduction ofacidity can well be anticipated from the fact that alkylsulfonic acidhas higher acidity than benzenesulfonic acid and also aliphaticcarboxylic acids have higher acidity than benzoic acid.

(2) The chelate-forming functional group may not fully show its chelateforming ability because its free movement is restricted. Also, as thechelate-forming functional group is subject to the influence of benzenering through the short chain, no satisfactory heat resistance may beobtained.

When A is a Long-Chain Group Like Nonylene

(1) Molecular weight of the cation exchanger is enlarged, so that theion exchange capacity per unit weight may be reduced.

(2) Long chain is advantageous from the viewpoint of improvement ofchelate forming ability, but the molecular weight of chelate resin isenlarged, so that the chelate forming ability per unit weight may bereduced.

In the present invention, it is preferable for production of theobjective substance that A is introduced to the m- or p-position of thestyrene residue. Although little influence is expected to be given tothe steric relation between benzene ring and substituent group (L beingSO₃ ⁻ group or chelate- forming functional group) even when A isintroduced to the opposition, it is preferable to introduce A to the m-or p-position in consideration of possible steric hindrance incopolymerization with a crosslinking agent.

The alkyl groups which may substitute the benzene ring include methyland ethyl, and the substituent halogen atoms include fluorine, chlorine,bromine and iodine.

Examples of the crosslinkable monomers having unsaturated hydrocarbongroups include divinylbenzene, polyvinylbenzene, alkyldivinylbenzene,dialkyldivinylbenzene, ethylene glycol (poly)(meth)acrylate,polyethylene glycol di(meth)acrylate, (poly)ethylenebis(meth)acrylamide,and the like of these monomers, divinylbenzene is preferred.

In the cation exchanger or chelating agent of the present invention, thepercentages of the structural units represented by the formula (I) andthe structural units derived from a crosslinkable monomer having anunsaturated hydrocarbon group are not specifically defined. It isnotable, however, that a too small ratio of the structural unitsrepresented by the formula (I) leads to a reduction of ion exchangecapacity or chelating ability (exchange capacity) per unit weight, whilea too small percentage of the structural units derived from acrosslinkable monomer having an unsaturated hydrocarbon group results ina high swelling tendency to cause a decrease of ion exchange capacity orchelating ability (exchange capacity) per unit weight. Therefore, thepercentages of the respective structural units should be properlyselected by taking into account ion exchange capacity, chelating ability(exchange capacity), swelling tendency, strength and other factors.

It is, however, preferable that the percentage of the structural units(precursor monomer) represented by the formula (I) in the wholestructural units (whole precursor monomers) constituting the cationexchanger or chelating agent is usually 5 to 99 mol %, preferably 50 to99 mol %, and the percentage of the structural units (precursor monomer)derived from a crosslinkable monomer having an unsaturated hydrocarbongroup is usually 0.1 to 50 mol %, preferably 0.2 to 25 mol %.

The neutral salt decomposition capacity per unit weight of the cationexchanger of the present invention is usually 1.0 to 6.0 meq/g,preferably 1.0 to 5.5 meq/g, and its ion exchange capacity per unitweight, although variable depending on the water content, is usually 0.1to 2.1 meq/ml. Here, the symbol “meq/g” denotes milliequivalent per unitweight of dry resin, the symbol “meq/ml” denotes milliequivalent perunit volume of hydrous resin.

The exchange capacity per unit weight of the chelate resin of thepresent invention is usually 1.0 to 6.0 meq/g, preferably 1.0 to 5.5meq/g, and its exchange capacity per unit volume, although variabledepending on water content, is usually 0.1 to 2.1 meq/g. Here, thesymbol “meq/g” denotes milliequivalent per unit weight of dry resin, andthe symbol “meq/ml” denotes milliequivalent per unit volume of hydrousresin.

Next, a process for producing the cation exchanger according to thepresent invention is described.

The cation exchanger of the present invention can be produced bysuspension polymerizing at least a precursor monomer having thestructural units represented by the formula (II) and a crosslinkablemonomer having an unsaturated hydrocarbon group in the presence of apolymerization initiator, and if necessary introducing a cation exchangegroup into the obtained spherical crosslinked polymer.

The structural unit represented by the formula (II) is a precursor ofthe structural unit represented by the formula (I) (where L is SO₃ ⁻X⁺).In the formula (II), A has the same meaning as defined in the formula(I), Z¹ represents chlorine, bromine, iodine, a hydroxyl group, a tosylgroup (toluenesulfonic group), a thiol group or a sulfonic group, andthe benzene ring may be substituted with an alkyl group or a halogenatom. Introduction of a cation exchange group is required in case whereZ¹ is a substituent group other than sulfonic group.

The precursor monomers of the structural units represented by theformula (II) where A is an alkylene group (alkyl spacer type monomers)can be synthesized, for example, in the following way: a halogenatedstyrene (such as chlorostyrene or bromostyrene), a chloromethylstyrene(which may be a mixture of m-form and p-form) or a vinylphenetyl halideis reacted with a metallic magnesium to obtain a Grignard reagent andthe latter is coupled with 1, ω-dihalogenoalkane.

In the coupling reaction, a catalyst such as a copper halide (copperchloride, copper bromide or copper iodide), Li₂CuCl₄ or an amine may beused to carry out the reaction efficiently. An alkyl spacer type monomercan also be synthesized by a method in which a ω-halogenoalkylbenzenederivative is acetylated and then a vinyl group is introduced.

The precursor monomers of the structural units represented by theformula (II) where A is an alkoxymethylene group (ether spacer typemonomers) can be synthesized, for example, in the following way: avinylbenzyl alcohol is reacted with 1, ω-dihalogenoalkane to convertinto a halogenoalkoxymethylstyrene derivative.

Suspension polymerization is carried out with a suspension containing aprecursor monomer of the structural units represented by the formula(II) and a crosslinkable monomer having an unsaturated hydrocarbongroup. In this case, if necessary a third monomer may be used as acopolymerization component within limits not lowering the function ofthe produced cation exchanger of the present invention.

As the copolymerization component, there can be used, for example,styrene, alkylstyrene, polyalkylstyrene, (meth)acrylic ester,(meth)acrylic acid, acrylonitrile and the like, in an amount of usuallynot more than 50 mol %, preferably not more than 20 mol %, based on thetotal amount of the essential monomers. The byproducts in the synthesisof the precursor monomers of the structural units represented by theformula (II), such as bisvinylphenylethane, bisvinybenzylether andbisvinylphenylbutane, can also be used as crosslinking agent.

A known water-in-oil type or oil-in-water type suspension polymerizationmethod can be employed for the suspension polymerization in the presentinvention. In this suspension polymerization, the bath ratio of water tooil or oil to water is preferably adjusted to fall in the range from 1:2to 1:6. As the polymerization initiator, there can be used any pertinenttype of polymerization initiators such as peroxide type and azo type,specifically such peroxide type polymerization initiators as benzoylperoxide (BPO), lauroyl peroxide and t-butyl hydroperoxide, and such azotype polymerization initiators as azoisobutylnitrile (AIBN) and2,2′-azobis(2,4-dimethylvaleronitrile).

The amount of the polymerization initiator used for the reaction isusually 0.1 to 3 wt % based on the overall amount of the monomers.Polymerization temperature depends on half-value period temperature andcontent of the polymerization initiator used, polymerizability of themonomers and other factors, but is usually 40 to 150° C., preferably 50to 100° C. Polymerization time is usually one to 30 hours, preferablyone to 15 hours.

In the suspension polymerization, various types of solvent may be addedas required. The physical structure of the obtained crosslinkedcopolymer particles differs depending on the kind and amount of thesolvent used, so that it is possible to obtain the preferred type, suchas gel type or porous type, of crosslinked copolymer particles bycontrolling the solvent used.

For instance, in case where suspension polymerization is carried out byadding an organic solvent such as toluene, hexane, isooctane,2-ethylhexanol or the like which is a poor solvent for the precursormonomers of the structural units represented by the formula (II), therecan be obtained the crosslinked copolymer particles of a porousstructure although the product is variable depending on the monomercontent in the suspension polymerization system. On the other hand, incase where a good solvent such as tetrahydrofuran, 1,4-dioxane or thelike is used, there can be obtained the crosslinked copolymer particleswith a swelling tendency. It is also possible to add other types ofsolvent such as water, methanol, ethanol, acetone or the like. Theamount of such a solvent added is usually not more than 200 wt % basedon the total amount of the monomers.

The size of the obtained crosslinked polymer particles may differ in amanner according to the purpose of use of the cation exchanger. In casewhere it is used as an ion exchange resin, the average particle size isusually 50 μm to 2 mm, and in case where it is used as a resin forcatalysts, the average particle size is usually 20 μm to 1 mm.

In the production process of the present invention, in case where Z¹ inthe formula (II) is a substituent group other than sulfonic group, acation exchange group (sulfonic group in the formula (II)) is introducedby a known method (sulfonation reaction). Such sulfonation reaction canbe effected, for example, by the following methods when Z¹ is a halogenatom:

(1) The polymerization product is reacted with thiourea to obtain anisothiouronium salt and then the product is oxidized with hydrogenperoxide or the like to convert the substituent into sulfonic group.

(2) The polymerization product is reacted with EtOCS₂K to obtain adithiocarbonic acid-O-ethyl ester and then the product is oxidized toconvert the substituent into sulfonic group.

(3) The polymerization product is reacted with CH₃COSH to obtain anacetic thioester and then the product is oxidized to covert thesubstituent into sulfonic group.

(4) In case where Z¹ for introducing a sulfonic group through reactionwith sodium sulfite is a thiol group, the polymerization product may beoxidized to convert the substituent into sulfonic group.

In the above reaction, usually a solvent is added to the reaction systemfor swelling the crosslinked polymer particles. As the solvent, therecan be used, for example, water, alcohols such as methanol, ethanol andpropanol, hydrocarbons such as toluene and hexane, chlorine typehydrocarbons such as dichloromethane and 1,2-dichloroethane, ethers suchas dibutyl ether, dioxane and tetrahydrofuran, and others such asdimethylformamide and acetonitrile. Reaction temperature depends on themode of reaction, the kind of the functional group and solvent used andother factors, but is usually 20 to 130° C.

The cation exchanger of the present invention is obtained in sphericalform because of use of suspension polymerization described above, butthe product may be pulverized into powders. It is also possible toobtain the product in various other forms such as lumpy, fibrous, filmy,etc., by using solution polymerization.

Besides the above-described monomer method, the cation exchanger of thepresent invention can also be produced by a method in which achloromethylated crosslinked copolymer is used as starting material andthe substituent group A is introduced by polymeric modification method.More specifically, a method can be used in which a reagent such asn-BuLi is acted to a chloromethylated crosslinked polystyrene to producethe vinylbenzyl anions and the said anion are reacted with 1,ω-dihalogenoalkane to obtain an alkyl spacer type crosslinked copolymer.According to the same method as described in the above, the introductionof sulfonic group can be conducted. However, the above-described monomermethod is preferred because of higher ion exchange capacity of theobtained cation exchanger.

Now, a process for producing the chelating agent according to thepresent invention is explained. The chelating agent of the presentinvention can be produced by suspension polymerizing a precursor monomercomprising the structural units represented by the formula (III) and acrosslinkable monomer having an unsaturated hydrocarbon group in thepresence of a polymerization initiator, and introducing achelate-forming functional group into the obtained spherical crosslinkedpolymer. The precursor monomer of the structural units represented bythe formula (III) is a precursor of the monomer of the structural unitsrepresented by the formula (I) (where L is a chelate-forming functionalgroup). In the formula (III), A has the same meaning as defined in theformula (I), Z² represents chlorine, bromine, iodine or a hydroxylgroup, and the benzene ring may be substituted with an alkyl group or ahalogen atom.

In the process for producing the chelating agent, there are used thesame monomer method and polymeric modification method as explained inthe above-described process for producing the cation exchanger, and thesame conditions can be used except for introduction of a chelate-formingfunctional group in place of a cation exchange group. That is, in themonomer method, the operations till suspension polymerization can beconducted in the completely same way as in the above-described processfor producing the cation exchanger to obtain the crosslinked polymerparticles. In this case, the average size of the crosslinked polymerparticles is usually in the range of 50 μm to 2 mm.

Introduction of the chelate-forming functional group into the sphericalcrosslinked polymer can be accomplished according to a conventionalmethod. For instance, in case where Z² is a halogen atom, adimethylglycine type chelate resin can be obtained by reacting adimethylglycine ester and hydrolyzing the reaction product. Similarly,an iminodiacetate type chelate resin can be obtained by reacting animinodiacetic ester and hydrolyzing the reaction product. In case whereZ² is a hydroxyl group, it is also possible to introduce various kindsof chelate-forming functional group into the spherical crosslinkedpolymer according to a known reaction scheme.

In the above reaction, usually a solvent is added to the reaction systemfor bloating the crosslinked polymer particles. As the solvent, therecan be used those used in the sulfonation reaction described above.Reaction temperature is variable depending on the mode of reaction, thekind of the functional group and solvent used and other factors, but itis usually 20 to 130° C.

Introduction of a chelate-forming functional group can be accomplishedin the same way as in case where the polymeric modification method isused. The monomer method is preferred to the polymeric modificationmethod as in the case of the cation exchanger.

The chelating agent of the present invention is obtained as a sphericalproduct when using suspension polymerization as in the above-describedembodiment, but it may be pulverized into powders. It is also possibleto obtain the agent in various other forms, such as lumpy, fibrous,filmy, etc., by using solution polymerization.

According to the present invention, as described above, there isprovided a cation exchanger or a chelating agent of a novel structure.

The cation exchanger of the present invention finds a wide range of use.The common uses thereof are, for instance, general-purpose watertreatments (softening of hard water, production of pure water, recoveryand separation of metals, purification of amino-acids, etc.), separationand purification of saccharic solutions, purification ofpharmaceuticals, adsorption removal of colloidal substances such asiron, dehydration, and separation and purification of weakly acidicsubstances. Among other uses is preparation of various types ofadsorbents, such as those for chromatographic carriers, film materials,catalyst carriers, phase-transfer catalysts, enzymes, cells, bacterialcell immobilization carriers, etc. It is especially remarkable thatthanks to its excellent heat resistance, the cation exchanger of thepresent invention is particularly advantageous for use at hightemperatures, for instance, in use as a catalyst.

Further, the cation exchanger of the present invention, as apparent fromthe Examples described below, has the advantage of being minimized inelution from resins, which is a defect of the conventional cationexchangers, and hence almost free of offensive smell.

On the other hand, the chelating agent of the present invention iscapable of capturing a wide variety of metallic ions by proper selectionof the chelate-forming functional group.

Furthermore, the chelating agent of the present invention has excellentchelate forming ability and heat resistance as well as the advantage ofbeing minimized in elution from resins and hence almost free ofoffensive smell.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is hereinafter described more particularly byshowing the examples thereof, which examples however are merely intendedto be illustrative and not to be construed as limiting the scope of theinvention.

EXAMPLE 1 Cation Exchanger Synthesis of 4-Bromobutylstyrene

44 g of metallic Mg and 360 g of tetrahydrofuran (THF) were suppliedinto a one-litre flask equipped with a nitrogen gas introducing tube, aDimroth condenser, a ramified isotactic dropping funnel and a stirrer,and the internal temperature was set at 36° C. Then 350 ml of a THFsolution of 251 g of p-chlorostyrene was added dropwise to the flaskover a period of 2 hours under the conditions that the internaltemperature doe not become higher than 40° C., to prepare a Grignardsolution of p-chlorostyrene. Meanwhile, a mixed solution of 1,060 g of1,4-dibromoethane, 400 ml of THF and 7.5 g of Li₂CuCl₄ was prepared.

The said Grignard solution was added dropwise to the said dibromoethanesolution over a period of 2 hours under the conditions that the internaltemperature does not become higher than 40° C. After the dropwiseaddition, the mixed solution was stirred for 2 hours to complete thereaction. The reaction solution was poured into water and then theliquid phase was separated. The organic phase was taken out and THF wasdistilled away under reduced pressure. The residue was subjected tovacuum distillation to recover the objective substance4-bromobutylstyrene (a slightly yellowish transparent liquid having aboiling point of 130° C./0.5 mmHg).

Synthesis of 4-Bromobutylstyrene Crosslinked Copolymer

200 ml of desalted water and 50 ml of a 2 wt % polyvinyl alcoholsolution were added to a 500 ml flask equipped with a nitrogen gasintroducing tube, a stirrer and a condenser, and nitrogen was introducedinto the mixed solution to remove oxygen present therein. Meanwhile,48.0 g of 4-bromobutylstyrene, 1.08 g of divinylbenzene (with purity of100 wt %) and 0.4 g of AIBN were mixed and dissolved to prepare amonomer solution and oxygen existing therein was removed in the same wayas described above.

This monomer solution was put into the said flask and stirred at 150 rpmto prepare a suspension. The suspension was stirred at room temperaturefor 30 minutes, then heated to 70° C. and further stirred for 18 hoursto effectuate suspension polymerization to obtain a light-yellowtransparent spherical polymer. The produced polymer was taken out,washed with water and further cleaned thrice with methanol. Thepolymerization yield was 93 wt % and the initial degree of crosslinkingof the polymer was 4 mol %.

Sulfonation of 4-Bromobutylstyrene Crosslinked Copolymer

25 g of the said polymer was supplied into a 500 ml flask equipped witha stirrer and a condenser, and 150 ml of ethanol was added thereto andstirred at room temperature. Then 22 g of thiourea was added to carryout the reaction at 70° C. for 8 hours. After the reaction, the reactionproduct was taken out and washed with water, and then 100 ml of a 30 wt% hydrogen peroxide solution was added thereto, carrying out thereaction under stirring at 50° C. for 6 hours to obtain a cationexchange resin. The results of determination of the general capabilitiesof this cation exchange resin were as shown in Table 1.

TABLE 1 Salt-splitting capacity 3.38 meq/g Salt-splitting capacity 1.35meq/ml Water content 51.2 wt %

EXAMPLE 2 Cation Exchanger Synthesis of 4-Bromobutoxymethylstyrene

20 g (0.5 mol) of sodium hydroxide and 20 ml of water were added to a300 ml flask equipped with a stirrer and a condenser, and stirred toform a homogeneous solution. The solution temperature was returned toroom temperature.

13.42 g (0.1 mol) of hydroxymethylstyrene (a mixture of m-form andp-form), 32.39 g (0.15 mol) of 1,4-dibromobutane and 3.22 g (0.01 mol)of tetrabutylammonium bromide were dissolved in 100 ml of toluene andsupplied into the said flask, and the mixed solution in the flask wasstirred and reacted at 40° C. for 6 hours.

After the reaction, the organic phase was separated and washed withwater. This organic phase was dried over magnesium sulfate and toluenewas distilled away under reduced pressure. The resulting solution wassubjected to vacuum distillation in the presence ofdiphenylpicryl-2-hydrazyl (DPPH) to obtain a colorless transparentsolution (b.p. 112-117° C./0.6 mmHg). The structure of this solution wasconfirmed by NMR analysis. The yield of 4-bromobutoxymethylstyrene was15.0 g (56 wt %).

Synthesis of 4-Bromobutoxymethylstyrene Crosslinked Copolymer

The same procedure as defined in Example 1 was conducted except for useof the said 4-bromobutoxymethylstyrene to obtain a4-bromobutoxymethylstyrene crosslinked copolymer.

Sulfonation of 4-Bromobutoxymethylstyrene Crosslinked Copolymer

The same procedure as defined in Example 1 was conducted except that thesaid 4-bromobutoxymethylstyrene crosslinked copolymer was used, that 27g of EtOS₂K was used in place of thiourea, and that a dithiocarbonicacid O-ethyl ester was yielded as the intermediate product, to obtain acation exchange resin. The results of determination of the generalcapabilities of this cation exchange resin were as shown in Table 2.

TABLE 2 Salt-splitting capacity 3.18 meq/g Salt-splitting capacity 1.10meq/ml Water content 52.7 wt %

Heat Resistance Test of Cation Exchange Resin

Over the cation exchange resin obtained in Example 1 was passed 10 timesas much amount of a 4 wt % sodium chloride solution as the said resin toturn the counter ions into Na form, and a prescribed amount of the resinwas weighed out. Then 500 ml of a 2N hydrochloric acid solution waspassed over this resin to regenerate the H form, and the volume of theresin was measured. This regenerated form of resin was put into aglass-made autoclave, to which 0.8 times as much volume of desaltedwater as the H-form resin was added. In order to remove oxygen presentin the solution in the container, nitrogen gas was passed through thesolution in a 50° C. heated condition for 60 minutes. Then the autoclavewas immersed in an oil bath and left at 150° C. for 30 days. Thereafter,for the sake of confirmation, the resin was regenerated to H type with500 ml of a 2N hydrochloric acid solution and the volume of the resinwas measured. Further, a 4 wt % sodium chloride solution of an amount 5times the resin was passed over the resin to convert the counter ions X⁻into Na form.

Retention (wt %) of alkylene chain A in the resin was determined by thecalculation formula shown below. Symbol A in the calculation formuladesignates salt-splitting capacity (meq/ml) and symbol B indicates thevolume (ml) of the H-form resin. The results are shown in Table 3. The“comparative resin” in Table 3 is a commercial cation exchange resin“Diaion SK-1B” (registered trade name) available from MitsubishiChemical Corporation.

Retention (wt %)=[(A after test×B after test)÷(A before test×B beforetest)]×100

TABLE 3 Resin of Example 1 resin Comparative Volumetric change 70.2→68.970.7→66.5 of resin Change of salt- 1.35→1.28 2.03→1.76 splittingcapacity Retention (wt %) 93 82

EXAMPLE 3 Dimethylglycine Type Chelate Resin Introduction ofChelate-forming Functional Group into Crosslinked Copolymer

10 g of a polymer (4-bromobutylstyrene crosslinked copolymer) obtainedin the same way as in Example 1 was supplied into a 300 ml flaskequipped with a stirrer and a condenser, then 40 ml of 1,4-dioxane wasadded and the solution was stirred at room temperature for 30 minutes.Thereafter, 20 ml of dimethylglycine ethyl ester was added to carry outesterification reaction under stirring at 70° C. for 6 hours. Thereaction solution was passed through a glass filter and transferred intoanother flask equipped with a stirrer and a condenser, to which 150 mlof a 2N NaOH solution was added for reacting at 50° C. for 3 hours toeffectuate hydrolysis of the ester to obtain a dimethylglycine typechelate resin. The obtained chelate resin was taken out and washed withwater, and its general capabilities were determined. The results showedthat the exchange capacity of the resin was 0.87 meq/ml (2.39 meq/g) andthe water content was 48.4 wt %.

EXAMPLE 4 Dimethylglycine Type Chelate Resin Synthesis of4-Bromopropylstyrene Crosslinked Polymer

The same procedure as defined in Example 1 was conducted except that 687g (4.39 mol) of 1,3-dibromopropane was used in place of1,4-dibromobutane to obtain 4-bromopropylstyrene (a light-yellowtransparent solution, b.p. 118° C./0.2 mmHg). This 4-bromopropylstyrenewas further treated in the same way as in Example 1 to obtain alight-yellow transparent spherical polymer with an initial degree ofcrosslinking of 5 mol %.

Introduction of Chelate-forming Functional Group into CrosslinkedCopolymer

The same procedure as defined in Example 3 was conducted except for useof the polymer obtained from the above synthesis to obtain adimethylglycine type chelate resin. The exchange capacity of theobtained chelate resin was 0.96 meq/ml (2.75 meq/g) and its watercontent was 49.2 wt %.

EXAMPLE 5 Dimethylalycine Type Chelate Resin Introduction ofChelate-forming Functional Group into Crosslinked Copolymer

The same procedure as defined in Example 3 was conducted except for useof the polymer (4-bromobutoxymethylstyrene crosslinked copolymer)obtained in the same way as in Example 2 to obtain a dimethylglycinetype chelate resin. The exchange capacity of the obtained chelate resinwas 0.74 meq/ml (2.21 meq/g) and its water content was 55.3 wt %.

EXAMPLE 6 Iminodiacetate Type Chelate Resin Introduction ofChelate-forming Functional Group into Crosslinked Copolymer

10 g of a 4-bromopropylstyrene crosslinked copolymer obtained in thesame way as in Example 4 was supplied into a 300 ml flask equipped witha stirrer and a condenser, and 50 ml of 1,4-dioxane was added theretoand stirred at room temperature for 30 minutes. Then 30 g of animinodiacetic ester was added to carry out the esterification reactionunder stirring at 80° C. for 3 hours. The reaction solution was passedthrough a glass filter and transferred into another flask equipped witha stirrer and a condenser, and 150 ml of a 2N NaOH solution was addedfor reacting at 70° C. for 5 hours to effectuate hydrolysis of the esterto obtain an iminodiacetate type chelate resin. The obtained chelateresin was taken out and washed with water, and its general capabilitieswere determined. The result showed that the exchange capacity of theresin was 0.87 meq/ml (2.39 meq/g) and its water content was 48.4 wt %.

EXAMPLE 7 Aminophoshoric Acid Type Chelate Resin Introduction ofChelate-forming Functional Group into Crosslinked Copolymer

100 g of a polymer (4-bromobutylstyrene crosslinked copolymer) obtainedin the same way as in Example 1, 300 ml of toluene and 120 g ofethylenediamine were supplied into a one-litre flask equipped with astirrer and a condenser, and the mixed solution was heated to 70° C. tocarry out the amination reaction for 6 hours to obtain anaminoethylaminobutyl group-terminated crosslinked copolymer. After thecompletion of the reaction, the reaction product was cooled down tonormal temperature and the aminated crosslinked copolymer was filteredout and washed with methanol, after which toluene was removed.

Then 100 g of the hydro-extracted aminated crosslinked copolymer, 40 mlof concentrated sulfuric acid, 35 ml of a 37 wt % formaldehyde solution,46 g of phosphorous acid and 30 ml of desalted water were supplied intoanother flask equipped with a stirrer and a condenser, and the mixedsolution was heated to 100° C. to carry out the phosphoration reactionfor 5 hours to obtain an aminophosphoric acid type chelate resin. Theobtained resin was washed with desalted water and its calcium exchangecapacity was determined.

Determination of Calcium Exchange Capacity

A 200 mM trishydrochloric buffer solution (pH 8.0) of 50 mM calciumchloride was prepared in a 300 ml Erlenmeyer flask. Meanwhile, theaminophosphoric acid type chelate resin was immersed in a 2N NaOHsolution and washed with desalted water, and 5.0 ml of the solution wascollected accurately. Then the dehydo-extracted resin was put into thebuffer solution, and after 20-hour shaking at room temperature, 5 ml ofthe supernatant solution was collected and titrated with 10 mM disodiumethylenediaminetetraacetate. Calcium exchange capacity was determinedfrom the residual amount of calcium. Calcium exchange capacity of theaminated crosslinked copolymer was 1.17 meq/ml-resin.

EXAMPLE 8 Phosphonic Acid Type Chelate Resin Synthesis of4-Chlorobutylstyrene

134 g of metallic Mg was put into a 3-litre flask equipped with anitrogen gas introducing tube, a Dimroth condenser, a ramified isostaticdropping funnel and a stirrer, and the internal temperature was set at31° C. Then a solution of 554 g of chlorostyrene, 739 g of THF and 1,133g of toluene was added dropwise over a period of 2 hours to obtain aGrignard reagent of chlorostyrene.

Meanwhile, 12 g of cupric chloride, 150 g of THF and 1,345 g of4-bromo-1-chlorobutane were supplied into a separately prepared reactionvessel, and the internal temperature was set at 25° C.

Then the said Grignard reagent was added dropwise into the said reactionvessel over a period of 3 hours under the conditions that the internaltemperature would become 30° C. After the end of the dropwise addition,the solution was stirred at 30° C. for 3 hours to complete the reaction.The reaction solution was poured into water and the liquid phase wasseparated. The organic phase was taken out, and THF, toluene andresidual 4-bromo-1-chlorobutane were distilled away under reducedpressure to obtain the objective substance 4-chlorobutylstyrene.

Synthesis of 4-Chlorobutylstyrene Crosslinked Copolymer

500 ml of desalted water, 2 g of polyvinyl alcohol and 40 g of anhydroussodium sulfate were supplied into a 500 ml flask equipped with anitrogen gas introducing tube and a condenser, and nitrogen gas wasintroduced into the flask to remove oxygen present in the solution.Meanwhile, 30 ml of 2-ethylhexyl alcohol and 0.5 g of AIBN were added toa mixture of 25.8 ml of 4-chlorobutylstyrene and 4.2 ml ofdivinylbenzene (purity: 55 weight %) to prepare a monomer solution, andoxygen existing therein was removed in the same way as described above.

The monomer solution was put into the said flask and stirred at 150 rpmto prepare a suspension. The suspension was stirred at room temperaturefor 30 minutes, then heated to 70° C. and stirred for 6 hours, andfurther stirred at 100° C. for 2 hours to carry out suspensionpolymerization. The obtained polymer was taken out, washed three timeswith hot water and then immersed in methanol for a day. The resultingproduct was filtered out, air-dried and further dried in vacuo at 40° C.for 24 hours. The initial degree of crosslinking of the produced polymerwas 10 mol %.

Introduction of Chelate-forming Functional Group into CrosslinkedCopolymer

2.25 g of AlCl₃ and 5 ml of PCl₃ were supplied into a 300 ml flaskequipped with a stirrer and a condenser and reacted under reflux at 80°C. for 24 hours. After the end of the reaction, the reaction mixture waspoured into an ice-water bath to decompose the unreacted materials toobtain a phosphonic acid type chelate resin. The obtained chelate resinwas immersed overnight in a 2N NaOH solution and then the solution wassubstituted with a 1N HCl solution several times. The product was washedwith desalted water until the washings became neutral, and thenair-dried. Thereafter, phosphorus content and cation exchange capacitywere determined by the methods described below. The results are shown inTable 4. The vacuum-dried chelate resin was used for the determinations.

Determination of Phosphorus Content

0.05 g of the chelate resin was supplied into a Kjeldahl flask, then 5ml of concentrated nitric acid was added and the mixture was heatedslowly until the brown vapor turned white with caution so as not tocause bumping, and then allowed to cool. Thereafter, 5 ml of 60° C.perchloric acid was added and the mixture was heated over low or mediumheat until the resin was decomposed. After additional 2- to 3-hourheating and succeeding cooling, the solution in the flask wastransferred into a graduated flask and diluted to the mark with desaltedwater.

5 ml of this solution was put into a 50 ml graduated flask, one drop ofphenolphthalein was added thereto and then 5 ml of a dilute ammoniasolution was added until the mixed solution assumed a slight crimsoncolor. Thereafter, a 5N nitric acid solution, 5 ml of a 0.25 wt %ammonium metavanadate solution and 5 ml of a 5 wt % ammonium molybdenatesolution were added successively and the mixed solution was diluted tothe mark with desalted water.

Absorbance at 440 nm of the obtained solution was measured by a visibleultraviolet spectrophotometer, and by using the calibration curvessimilarly prepared from a 1,000 ppm phosphorus standard solution, thephosphorus content was calculated from the following equation.

Phosphorus content (wt %)=A×B×C×100

A: phosphorus content (mg) in the measuring solution determined from thecalibration curves

B: total amount (ml) of the specimen solution/amount (ml) of thespecimen solution used for colorimetry

C: 0.001/amount (g) of the resin used for the measurement

Determination of Cation Exchange Capacity

150 ml of 0.1N-NaOH-1M-NaCl was added to 0.25 g of the H type resin andshaken at 30° C. for 48 hours. After shaking, the amount of NaOH in thesupernatant was measured by neutralization titration with a 0.1N HClsolution of the known factor, and the ion exchange capacity wascalculated from the following equation. Methyl orange was used asindicator.

Cation exchange capacity (meq/g)=0.1×f×(B−A)×(V/v)×(1/w)

A: titer (ml) of the 0.1N HCl solution required for neutralization ofthe specimen

B: titer (ml) of the 0.1N HCl solution required for the blank test

f: factor of the 0.1N HCl solution

V: total amount (ml) of the specimen solution

v: amount (ml) of the specimen solution used for the titration

W: amount (g) of the resin used for the titration

EXAMPLES 9-11

Phosphonic acid type chelate resins were obtained by conducting the sameprocedure as defined in Example 8 except that the reagent and thecatalyst used for the phosphonation reaction were changed as shown inTable 4, and the phosphorus content and cation exchange capacity of theobtained resins were determined in the same way as described above. Theresults are shown in Table 4.

TABLE 4 Phosphorus Cation exchange Reagent Catalyst content (wt %)capacity (meq/g) Example 8 PCl₃ AlCl₃ 2.71 3.90 Example 9 PCl₃ AlBr₃4.16 5.80 Example 10 PBr₃ AlCl₃ 4.56 8.04 Example 11 PBr₃ AlBr₃ 4.41Undetermined

What is claimed is:
 1. A cation exchanger or a chelating agent having atleast structural units represented by the following formula (I) andstructural units being derived from a crosslinkable monomer containingan unsaturated hydrocarbon group:

wherein A represents a C₄-C₉ alkoxymethylene group; L represents SO₃⁻X⁺, where X⁺ is a counter ion coordinated with the SO₃ ⁻ group, or achelate-forming functional group; and the benzene ring may besubstituted with an alkyl group or a halogen atom.
 2. A cation exchangeror a chelating agent according to claim 1, wherein A in the formula (I)is a C₅-C₇ alkoxymethylene group.
 3. A cation exchanger or a chelatingagent according to claim 1, wherein the crosslinkable monomer containingan unsaturated hydrocarbon group is divinylbenzene, and the percentageof the structural units represented by the formula (I) is 5 to 99 mol %based on the whole structural units and the percentage of the structuralunits derived from divinylbenzene is 0.1 to 50 mol % based on the wholestructural units.
 4. A process for producing a cation exchangeraccording to claim 1, which comprises suspension-polymerizing at least aprecursor monomer having the structural units represented by thefollowing formula (II) and a crosslinkable monomer having an unsaturatedhydrocarbon group in the presence of a polymerization initiator, and ifnecessary, introducing a cation exchange group into the obtainedcrosslinked polymer:

wherein A has the same meaning as defined in the formula (I); Z¹represents chlorine, bromine, iodine, a hydroxyl group, a tosyl group(toluenesulfonic group), a thiol group or a sulfonic group; and thebenzene ring may be substituted with an alkyl group or a halogen atom.5. A process for producing a chelating agent as defined in claim 1,which comprises suspension-polymerizing at least a precursor monomerhaving the structural units represented by the following formula (III)and a crosslinkable monomer having an unsaturated hydrocarbon group inthe presence of a polymerization initiator, and introducing achelate-forming functional group into the obtained crosslinked polymer:

wherein A has the same meaning as defined in the formula (I); Z²represents chlorine, bromine, iodine or a hydroxyl group; and thebenzene ring may be substituted with an alkyl group or a halogen atom.